This patch adds the most basic tab interaction metrics for tab groups.
As discussed in standup, we agreed to move the `remove_` class of
metrics into its own bug due to extra complexity involved in correctly
capturing these events.
One other thing we discussed was what the scope of events should be for
the `close_` class of events, i.e. should we *only* capture an event
when someone clicks the "X" button or closes from the TOM menu, or
should we also account for things like context menus, keyboard
shortcuts, etc.? Originally we agreed to capture _all_ tab close events
and mark any source that was not one of the above mentioned two as
unknown. However, after thinking about this more, I don't believe this
is the right approach. There are many places in the codebase where a tab
is closed but not because a user deliberately did it (e.g. when moving a
tab to a new window — this is actually done by creating a new tab in a
new window and closing the old). We currently don't distinguish between
user-initiated close actions, so it would take some time to find all
these places and exclude them.
I favour an explicit inclusion approach (which is what we are doing
elsewhere). In this patch I added events for:
- closing a tab from the "X" close button (`close_tabstrip`)
- closing a tab from the tab context menu (`close_tabstrip`)
- closing a tab from the TOM (`close_tabmenu`)
There are other places that could potentially be
addressed, so I suggest moving these to a follow-up bug and addressing
them for 139.
Differential Revision: https://phabricator.services.mozilla.com/D244915
4a0e2c38cc